So there you have it - ads are very likely going to be part of Gmail soon. After all, it seems almost silly to not monetize a core app with an absolutely massive install base - between 500 million and a billion. I just hope these ads won't be overly intrusive, and from the looks of things, the Gmail team is approaching the situation with care.

Tasteful, generic, non-intrusive advertising is a fair trade for offering either a service (such as mail) or news and information (such as here).
But! The precise moment they move from generic, context/venue based ads, to ads based on the all intrusive TRACKING of individual's habits, as it's Google's (and all the other filthy maggots who run trackers) want to do, they've gone too far. I'll never acquiesce.
Knowledge is power, so knowledge specific to you, is power over you. They don't need that power to offer you products.
That said, if all my fellow tech savvy types who are also capable of free and independent thought, are waiting for a point where the masses of asses will say when enough is enough on this totality of control and tracking front, you'll dry up and turn to dust (Apple's popularity is exhibit one). More likely, you as I, will continue to be dragged--kicking and screaming--into this surveillance state nightmare by the mechanism of the shrinking numbers of viable alternatives. This is by design. The "don't buy it or use it if you don't like it" excuse is only valid when there are alternatives that don't suck the same or more.
Seems as though "what sucks the least" choices are the hallmark of this new century.
Opt-Out while you still can.....